在坑內开孔时,由于开孔即接触到岩石因而一經加压,在粗徑上头就产生了摆动,并直接波及到鑽头,致使鑽孔开成楕圆形。同时,由于鑽窩中的岩石都身受放炮的震动,往往形成局部破碎、局部完整。当鑽至这来地段时,很容易使鑽孔歪斜。为此,我們应用了1～1.5公尺基台木一根(如图),用螺絲杆固定在孔位上,开孔时先鑽过基台 When a hole is made in the pit, the rocking occurs on the large diameter due to the opening being in contact with the rock, and the rocking occurs directly to the drill bit, causing the hole to become a billet. At the same time, as the rock in the pit are subjected to the shock of blasting, they often form partial crushing and partial integrity. When drilling to the lot, it is easy to skew the borehole. To this end, we use a 1 to 1.5 meters on the base of a wooden (Figure), with a screw rod fixed in the hole, the hole drilled first base